If you do not already have an ICD, you will undergo ICD placement as part of routine clinical care. You may undergo ICD placement up to 1 month (30 days) before randomization. An ICD (implantable cardioverter-defibrillator) is a small battery-powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation and ventricular tachycardia. The device is programmed to detect abnormal heart beats (cardiac arrhythmia) and correct it by delivering a jolt of electricity.